Pilot Study On Biological Enhancing Filtration For Removing Iron Manganese And Micro-Pollutant In The Groudwater

Groundwater is an important water source for people's life and industry in our country.Because the water pollution isn't under effective control,groundwater has been polluted more or less at some area.Owing to ammonia and CODMn exceeding the standard,adding to the native iron and manganese,groundwater became to a kind of compound micro-polluted groundwater.The removals of pollutants interacting increase large difficulty of groundwater treatment.So,removing iron,manganese,ammonia and CODMn has become an important topic of drinking water treatment.The experiment adopted aerate-filtering treatment,inoculated compound ascendant bacteria and enhanced filter purification function to treat the compound micro-polluted groundwater.The study is divided into three parts:first,rejuvenation and screening of iron and manganese oxidizing bacteria and nitrobacteria;second,composite test of iron and manganese oxidizing bacteria and nitrobacteria;third,pilot study on compound ascendant bacteria treating groundwater.Based on rejuvenation and acclimation of eight original iron and manganese oxidizing bacteria and nitrobacteria,screened out iron and manganese oxidizing bacteria T2,T3,T4,T5 and nitrobacteria X₂,which had good water purification effect.After 1 month's acclimation,iron and manganese oxidizing bacteria and nitrobacteria recovered their activity,and their water purifying capacity increased a lot.At the early acclimation the pollutants removal effect of iron and manganese oxidizing bacteria removed increased slowly,then began to be faster at middle period,after 20 days,removal rate growth became slowed again.The ammonia removal rate of nitrobacteria recovered to a higher level at the early acclimation,for example,X₂ increased from 9.0%to 34.9%at the 10th day of acclimation,and then got to slow until the end of acclimation.Complex biological system is necessary for actual filter,and it is impossible that there is only one kind of bacteria in it,but an ascendant combination.So,pairwise bacteria combination tests and integrated bacteria combination tests were carried out.After 20 integrated bacteria combination tests,fit out YMn the manganese removal rate after 48h:YMn=0.156+2.68X₁+1.33X₂-2.19X3-0.673X4+4.14X₁2-3.21X₂2-0.352X32-0.421X42+3.12X₁X₂+2.37X₁X3-1.30X₁X4+1.24X₂X3-1.13X₂X4+4.72X3X4By calculation,the optimum bacteria combination was T2:T3:T4:T5:X₂=0.36:0.19:0.06:0.31:0.08.After test,the water purifying capacity of optimum bacteria combination was better than others.The average removal rates of iron,manganese,ammonia and CODMn after 48h were 94.7%,66.6%and 58.6%,respectively.Inoculate the bacteria to the filter column in waterworks by the optimum bacteria combination proportion.During experiment the raw water iron concentrate was 0.23?1.3mg/L,manganese was 7.38?8.38mg/L,ammonia was 1.49?1.98mg/L,CODMn was 2.73?3.54mg/L.The result showed that the outflowing iron,manganese,ammonia and CODMn concentrate all reached the drinking standard.It was proved that removing iron,manganese,ammonia and CODMn in compound micro-polluted groundwater by drop aeration-biological filtration was feasible.Because of the high concentrate manganese in raw water,the manganese removal was most important.The media maturation time of inoculated the ascendant bacteria combination shorted obviously,which was reduced from normal 60?70 days to 40?50 days.This showed the water purifying capacity of ascendant bacteria combination.After the research on water purification effect along the filter bed,it was found that manganese and ammonia could be removed in the same space.Ammonia didn't restrained the biological manganese removal directly,and its main influence depended on the competition of DO.The effective removal spaces of manganese and ammonia coincide with each other.At 1m/h filter rate,manganese removal space was from 10?110cm,ammonia was from 0?110cm;at 3m/h filter rate,the spaces of them move down to about 40-150cm.DO is very important for removing iron,manganese,ammonia and CODMn simultaneously.Especially,the lack of DO at the middle and bottom of the filter bed,restrained the manganese removal effect seriously.